1. Field of the Invention
The present invention relates to a flip chip type of light-emitting semiconductor device that comprises layers using group III nitride formed on a sapphire substrate. Especially, the present invention relates to the device having a high luminous intensity and a low driving voltage.
2. Description of the Related Art
FIG. 7 shows a sectional view of a conventional flip chip type of light-emitting semiconductor 400. Each 101, 102, 103, 104, 105, 106, 120, 130, and 140 represents a sapphire substrate, a buffer layer of AlN or GaN, an n-type GaN layer, an emission layer, a p-type AlGaN layer, a p-type GaN layer, a positive electrode, a protective film, a negative electrode having a multi-layer structure, respectively. And the thick positive electrode 120 which is connected to the layer 106 is a metal layer having a thickness of 3000 Å and being formed by metals such as nickel (Ni) or cobalt (Co).
Conventionally, to reflect light emitted from an emission layer 104 toward a sapphire substrate 101 effectively, a thick metal electrode is used as a flip tip type positive electrode 120.
However, a problem persists in luminous intensity. In the conventional device, metals such as nickel (Ni) or cobalt (Co) has been used to form the thick positive electrode 120. As a result, a reflectivity of visible (violet, blue, and green) rays whose wavelength is in the range of 380 nm to 550 nm was insufficient, and the device could not obtain an adequate luminous intensity as a light-emitting semiconductor device. Therefore, further improvement has been required, as presently appreciated by the present inventors.